*     * @param array The original array.     * @param newLength The length you wish the new array to have.     * @return Array of newly desired length. If shorter than the     *         original, the trailing elements are truncated.     */    protected byte[] resizeByteArray(byte[] array, int newLength) {        byte[]  newArray = new byte[newLength];        int     oldLength = array.length;        System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));        return newArray;    }    /**     * Write an array of bytes into the pngBytes array.     * Note: This routine has the side effect of updating     * maxPos, the largest element written in the array.     * The array is resized by 1000 bytes or the length     * of the data to be written, whichever is larger.     *     * @param data The data to be written into pngBytes.     * @param offset The starting point to write to.     * @return The next place to be written to in the pngBytes array.     */    protected int writeBytes(byte[] data, int offset) {        maxPos = Math.max(maxPos, offset + data.length);        if (data.length + offset > pngBytes.length) {            pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, data.length));        }        System.arraycopy(data, 0, pngBytes, offset, data.length);        return offset + data.length;    }    /**     * Write an array of bytes into the pngBytes array, specifying number of bytes to write.     * Note: This routine has the side effect of updating     * maxPos, the largest element written in the array.     * The array is resized by 1000 bytes or the length     * of the data to be written, whichever is larger.     *     * @param data The data to be written into pngBytes.     * @param nBytes The number of bytes to be written.     * @param offset The starting point to write to.     * @return The next place to be written to in the pngBytes array.     */    protected int writeBytes(byte[] data, int nBytes, int offset) {        maxPos = Math.max(maxPos, offset + nBytes);        if (nBytes + offset > pngBytes.length) {            pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, nBytes));        }        System.arraycopy(data, 0, pngBytes, offset, nBytes);        return offset + nBytes;    }    /**     * Write a two-byte integer into the pngBytes array at a given position.     *     * @param n The integer to be written into pngBytes.     * @param offset The starting point to write to.     * @return The next place to be written to in the pngBytes array.     */    protected int writeInt2(int n, int offset) {        byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};        return writeBytes(temp, offset);    }    /**     * Write a four-byte integer into the pngBytes array at a given position.     *     * @param n The integer to be written into pngBytes.     * @param offset The starting point to write to.     * @return The next place to be written to in the pngBytes array.     */    protected int writeInt4(int n, int offset) {        byte[] temp = {(byte) ((n >> 24) & 0xff),                       (byte) ((n >> 16) & 0xff),                       (byte) ((n >> 8) & 0xff),                       (byte) (n & 0xff)};        return writeBytes(temp, offset);    }    /**     * Write a single byte into the pngBytes array at a given position.     *     * @param b The integer to be written into pngBytes.     * @param offset The starting point to write to.     * @return The next place to be written to in the pngBytes array.     */    protected int writeByte(int b, int offset) {        byte[] temp = {(byte) b};        return writeBytes(temp, offset);    }    /**     * Write a PNG "IHDR" chunk into the pngBytes array.     */    protected void writeHeader() {        int startPos;        startPos = bytePos = writeInt4(13, bytePos);        bytePos = writeBytes(IHDR, bytePos);        width = image.getWidth(null);        height = image.getHeight(null);        bytePos = writeInt4(width, bytePos);        bytePos = writeInt4(height, bytePos);        bytePos = writeByte(8, bytePos); // bit depth        bytePos = writeByte((encodeAlpha) ? 6 : 2, bytePos); // direct model        bytePos = writeByte(0, bytePos); // compression method        bytePos = writeByte(0, bytePos); // filter method        bytePos = writeByte(0, bytePos); // no interlace        crc.reset();        crc.update(pngBytes, startPos, bytePos - startPos);        crcValue = crc.getValue();        bytePos = writeInt4((int) crcValue, bytePos);    }    /**     * Perform "sub" filtering on the given row.     * Uses temporary array leftBytes to store the original values     * of the previous pixels.  The array is 16 bytes long, which     * will easily hold two-byte samples plus two-byte alpha.     *     * @param pixels The array holding the scan lines being built     * @param startPos Starting position within pixels of bytes to be filtered.     * @param width Width of a scanline in pixels.     */    protected void filterSub(byte[] pixels, int startPos, int width) {        int i;        int offset = bytesPerPixel;        int actualStart = startPos + offset;        int nBytes = width * bytesPerPixel;        int leftInsert = offset;        int leftExtract = 0;        for (i = actualStart; i < startPos + nBytes; i++) {            leftBytes[leftInsert] =  pixels[i];            pixels[i] = (byte) ((pixels[i] - leftBytes[leftExtract]) % 256);            leftInsert = (leftInsert + 1) % 0x0f;            leftExtract = (leftExtract + 1) % 0x0f;        }    }    /**     * Perform "up" filtering on the given row.     * Side effect: refills the prior row with current row     *     * @param pixels The array holding the scan lines being built     * @param startPos Starting position within pixels of bytes to be filtered.     * @param width Width of a scanline in pixels.     */    protected void filterUp(byte[] pixels, int startPos, int width) {        int     i, nBytes;        byte    currentByte;        nBytes = width * bytesPerPixel;        for (i = 0; i < nBytes; i++) {            currentByte = pixels[startPos + i];            pixels[startPos + i] = (byte) ((pixels[startPos  + i] - priorRow[i]) % 256);            priorRow[i] = currentByte;        }    }    /**     * Write the image data into the pngBytes array.     * This will write one or more PNG "IDAT" chunks. In order     * to conserve memory, this method grabs as many rows as will     * fit into 32K bytes, or the whole image; whichever is less.     *     *     * @return true if no errors; false if error grabbing pixels     */    protected boolean writeImageData() {        int rowsLeft = height;  // number of rows remaining to write        int startRow = 0;       // starting row to process this time through        int nRows;              // how many rows to grab at a time        byte[] scanLines;       // the scan lines to be compressed        int scanPos;            // where we are in the scan lines        int startPos;           // where this line's actual pixels start (used for filtering)        byte[] compressedLines; // the resultant compressed lines        int nCompressed;        // how big is the compressed area?        //int depth;              // color depth ( handle only 8 or 32 )        PixelGrabber pg;        bytesPerPixel = (encodeAlpha) ? 4 : 3;        Deflater scrunch = new Deflater(compressionLevel);        ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);        DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes, scrunch);        try {            while (rowsLeft > 0) {                nRows = Math.min(32767 / (width * (bytesPerPixel + 1)), rowsLeft);                nRows = Math.max( nRows, 1 );                int[] pixels = new int[width * nRows];                pg = new PixelGrabber(image, 0, startRow,                    width, nRows, pixels, 0, width);                try {                    pg.grabPixels();                }                catch (Exception e) {                    System.err.println("interrupted waiting for pixels!");                    return false;                }                if ((pg.getStatus() & ImageObserver.ABORT) != 0) {                    System.err.println("image fetch aborted or errored");                    return false;                }                /*                 * Create a data chunk. scanLines adds "nRows" for                 * the filter bytes.                 */                scanLines = new byte[width * nRows * bytesPerPixel +  nRows];                if (filter == FILTER_SUB) {                    leftBytes = new byte[16];                }                if (filter == FILTER_UP) {                    priorRow = new byte[width * bytesPerPixel];                }                scanPos = 0;                startPos = 1;                for (int i = 0; i < width * nRows; i++) {                    if (i % width == 0) {                        scanLines[scanPos++] = (byte) filter;                        startPos = scanPos;                    }                    scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);                    scanLines[scanPos++] = (byte) ((pixels[i] >>  8) & 0xff);                    scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);                    if (encodeAlpha) {                        scanLines[scanPos++] = (byte) ((pixels[i] >> 24) & 0xff);                    }                    if ((i % width == width - 1) && (filter != FILTER_NONE)) {                        if (filter == FILTER_SUB) {                            filterSub(scanLines, startPos, width);                        }                        if (filter == FILTER_UP) {                            filterUp(scanLines, startPos, width);                        }                    }                }                /*                 * Write these lines to the output area                 */                compBytes.write(scanLines, 0, scanPos);                startRow += nRows;                rowsLeft -= nRows;            }            compBytes.close();            /*             * Write the compressed bytes             */            compressedLines = outBytes.toByteArray();            nCompressed = compressedLines.length;            crc.reset();            bytePos = writeInt4(nCompressed, bytePos);            bytePos = writeBytes(IDAT, bytePos);            crc.update(IDAT);            bytePos = writeBytes(compressedLines, nCompressed, bytePos);            crc.update(compressedLines, 0, nCompressed);            crcValue = crc.getValue();            bytePos = writeInt4((int) crcValue, bytePos);            scrunch.finish();            return true;        }        catch (IOException e) {            System.err.println(e.toString());            return false;        }    }    /**     * Write a PNG "IEND" chunk into the pngBytes array.     */    protected void writeEnd() {        bytePos = writeInt4(0, bytePos);        bytePos = writeBytes(IEND, bytePos);        crc.reset();        crc.update(IEND);        crcValue = crc.getValue();        bytePos = writeInt4((int) crcValue, bytePos);    }}